Machine Controls Take Aim at the Job Shop
New CNCs, robot controls, and software enhancements help boost shop-floor productivity in job shops and high-end machining
By Patrick Waurzyniak
When machinists look at the latest CNC controls, they’re often wowed by the newest whiz-bang features for high-end, five-axis machining on complex aerospace parts or the CNCs typically found on highly complex multitasking machines. But focusing solely on those machine control systems can lead one to overlook the fact that the vast majority of daily machining tasks are performed on much more standard machines and CNCs typically found in job-shop environments.
Affordable new CNCs that target everyday machining for job shops and basic machine tools include the 808D Advanced CNC from Siemens Industry Inc. (Elk Grove Village, IL), announced in late February. The new Siemens 808D Advanced CNC for basic turning and milling machines adds to the company’s entry-level 808D line initially introduced at IMTS 2012, signaling the CNC builder’s commitment to the production-level end of the machining market.
Boom Times for Low-Cost CNCs
Another newer entry-level control is the Acu-Rite Millpwr G2 CNC from Heidenhain Corp. (Schaumburg, IL) that primarily targets new machines and retrofits of Bridgeport-style manual knee mills. “The concept is to create a CNC that is not scary, which is in line with our take on shop-floor programming,” said Chris Weber, national sales manager, Heidenhain Corp., of the company’s new G2 control. “We supply the drives, motors, ballscrews—everything you need. It’s a retrofit essentially for manual machines, an Everyman’s knee mill.”
The Heidenhain control, announced last October, offers three-axis milling with highly intuitive programming that prompts users with 3D graphics help steps to help maximize efficiency and production. The control is equipped with standard features including USB, networking accessibility, solid-model graphics and a 12.1" high-resolution display. The G2 features a 1-GHz processor and 2.5 GB of memory. Other enhancements include expanded tool and datum offsets for the more complicated jobs.
Users can disengage the quill, or Z axis, for 2.5-axis operation, noted Weber. “You’d be amazed at some of the shops we get into with this control, and you can use the machine completely manually, too,” he added. “Guys love it for part prototyping, and also in maintenance shops. The key is that it’s still a knee mill. The versatility of it allows you to do things that you can’t do with a machining center.”
Most job-shop environments are very cost-sensitive, noted Randy Pearson, dealer support manager, Machine Tool Systems, Siemens Industry Inc. The new Siemens 808D Advanced is designed for basic milling and turning machines. Affordably priced for machine tool builders, this CNC also offers a suite of features designed to improve machining accuracy, surface finish, safety and communication.
The control uses the same easy-to-use Sinumerik Operate interface offered on the existing Siemens 808D, 828D and 840D CNCs. “We’re using the same interface across the board, so it’s easier for users to switch between our controls and go from machine to machine,” Pearson noted. The control offers up to five axes/spindle motion control on a single machine channel, with drive bus communication between the CNC and drive for better position control. The 808D Advanced T is suitable for basic turning machines or turning centers without a Y axis, with the option of driven tools, while the Sinumerik 808D Advanced M offers advanced surface finish and the Sinamics V70 drive platform from Siemens, with an attractive price-to-performance ratio.
Scott Strache, senior product marketing engineer, Mitsubishi Electric Automation Inc. (Vernon Hills, IL), said there’s currently high demand for both the low end and the upper echelon of the CNC market. Mitsubishi Electric Automation sells a wide breadth of factory automation gear, and its CNCs range from the entry-level M70V control to the M700V CNC, serving the market for low-end machine tools to high-end five-axis machines, mill-turns, and Swiss-style machines, Strache said.
“What we’re seeing is that customers are looking for that bipolarization, a combination of the high end and the low-cost job shop controls,” said Strache. “There’s a lot of demand right now for the lower-cost machine, especially in the China market where that trend is really strong. With the low end, it all depends on not only the control platform, but also the drive series that they’re using, the size of the servo motors and the spindle motors.”
Some of Mitsubishi’s new hardware uses silicon carbide (SiC) technology in the power module for the drives, Strache said, which allows for high-speed switching. This allows the machine to run at higher rpm, he added, and improve machining productivity.
New CNC Programming Tools
Machine controls now offer users more refinement than in the past, noted Heidenhain’s Weber. “There are faster controls and great part finish,” Weber said, “that let you make parts faster, and make it better.” Some key new CNC routines, embedded programs, include Heidenhain’s Active Chatter Control and its recently introduced Trochoidal Milling cycle.
“What Trochoidal milling lets you do is do a circular move, milling a slot which is greater than the tool diameter in one pass, and it gives you more even wear on the tool, while speeding it up as much as 40%,” Weber said. “It’s even better when you combine that with adaptive feed control.” These control functions are aimed at automotive, aerospace, and medical applications, Weber added, for improved speed and part finishes.
CNC operators want more control and flexibility, noted Todd Drane, marketing manager, Fagor Automation Corp. (Elk Grove Village, IL). “Control is the best word I can use—control meaning the operator or programmer has complete control of any situation from the CNC keyboard during the execution process,” Drane said. “Operators are not just interested in starting and stopping a program for the various reasons, but they want the control to move forwards and backwards within the part program block by block, or to just jump anywhere and then resume the program execution.”
In addition, operators want the capability of background editing, access to modify the offsets, and automatically re-position the axes after a tool inspection during the program execution, he said. “These needs expand into shop-floor programming as well with the ability to quickly and easily create simple and complex profiles at the keyboard and automatically insert wherever they desire into the part program,” Drane said. “We have customers executing a part-program and then editing in the background a profile the part program will be executing later within the program.”
High accuracy without sacrificing speed is another key demand by CNC operators, Drane said. “The development of nanometric resolution linear encoders by Fagor has allowed us to offer customers exceptionally high programmable resolutions and accuracy,” he said. “In most cases, this added resolution assists in improved servomotor performance as well.”
Within the past year, Fagor introduced its HSSA (High Speed Surface Accuracy) feature, Drane said, an evolution of the high-speed cutting capabilities of Fagor’s CNC products. “The 8065 CNC will monitor the execution of the program in real time, while analyzing the micro segments of the programmed toolpath in order to achieve smooth and uniformed machine performance of both linear and rotary axes,” Drane said.
“The HSSA system will anticipate conflicting areas of the executing program and automatically smooth the transitions, while always following the machining toolpath,” he said. “At the same time, algorithms are developed for smoothing the profile while cross confirmation is done with the axes in respect to jerk control and the multiple acceleration/deceleration curves when the movement of a rotary axes requires a better response than the linear axes.”
Another recently developed Fagor feature is its Adaptive Real-time Feed and Speed control (ARFS), Drane said, in which the CNC analyzes the machining conditions such as spindle load, servo power, and tool-tip temperature, and automatically adapts both the axis feed rate and the spindle speed for maximum machining performance. “We initially saw a need for this feature in production environments simply because it allowed us to knock precious seconds off cycle times, while also increasing valuable tool life,” Drane said. “However, our customers are quickly finding additional benefits. The ARFS feature is easier on the machine axes of motion, particularly the spindle. One customer with a heavy-duty application is getting longer spindle bearing life since utilizing ARFS technology, and customers are learning from the QC department that part tolerances are coming in tighter.”
Better Metalcutting with Optimized Machines
In order to get the most performance out of machines and CNCs, machine shops need to spend time getting machine tools properly optimized, something many operators fail to do. An optimized machine cuts metal much faster and more accurately, but this usually requires getting help from qualified factory-trained personnel either at the machine builder or CNC developer.
“We help end users to optimize their solutions,” said Karl Kleppek, director of sales and marketing, CNCs, at the Hoffman Estates, IL-based CNC business unit of FANUC America Corp. (Rochester Hills, MI). “When you buy a machine tool, you need to understand what you bought and be able to put that into operation.”
A majority of machines typically are optimized to a standard, all-purpose level, Kleppek said, so they may not offer optimum performance for more specific machining applications. Optimizing machine accuracy can require using CNC compensation features including for backlash and backlash acceleration; pitch error; straightness compensation; temperature growth; and 3D error (volumetric) compensation. “We’ve been able to increase speed to improve productivity through process optimization,” Kleppek said. “Our 3DServoGuide allows us to tune the machine by comparing the actual programmed path and realized programmed path using the servo data at the tooltip.
“Is there an issue with the mechanics of the machine? Is it an issue with the programming? The process of drive tuning can really help identify a problem quickly and allow for correction action,” Kleppek said.
More CNC Robot Control
At AeroDef Manufacturing in February, Siemens demonstrated some new developments to CNC control of robots through the company’s mxAutomation solution from its partnership with Kuka Robotics. The added functionality will now allow robotic functions to be controlled on a second channel of the Sinumerik CNC and transferred to the robot via the Siemens PLC.
The new capability comes from a function called Run MyRobot, said Siemens’ Pearson. “Traditionally, you had to program the machines and then you teach the robot what it is going to be doing,” Pearson said. “With this new feature, it will allow an 840D-equipped machine, which is a multichannel machine, to use one of the channels to program and run the robot. Channel one runs the machine. And in a second channel you can have a toolchanger, automation or, in this case, a robot. It runs on the same hardware, so it’s one NC control, one HMI, and it has the ability to run the program at the same time, and talk to each other.”
With Run MyRobot, operators can program the CNC to control the robot for tasks such as robotic deburring, polishing or other machining operations. “They can use our hand-held unit to teach it, and it’s programmed in G-code at that time,” Pearson said, “so even an operator who has the basic understanding of programming parts can look at that and actually modify speeds or feeds of the robot at the same time.”
Last October, FANUC unveiled a CNC and robot integrated automotive architecture at the Rockwell Automation Fair, demonstrating connectivity to Rockwell Automation (Milwaukee) programmable automation controller (PAC) environments for easy-to-use, simplified automation solutions.
The FANUC-Rockwell partnership, which has been in place for about three years, focuses on cell control, safety and enterprise software, particularly for automotive powertrain applications, noted Kleppek. FANUC offers a pre-engineered integration automation solution for automotive powertrain applications, using an integrated safety network, a scalable machining cell control architecture comprised of multiple FANUC CNCs, robots, and Rockwell devices. Connections for FANUC CNCs and robots are included in Rockwell’s RSLogix 5000 software to quickly configure control and communication systems, and Ethernet/IP is the only network needed for connection of the cell controller to CNCs, robots or other devices.
“We’ve since received a round of very large orders, in the ballpark of 700–800 machines,” Kleppek said of an automotive foundry application for high-speed heavy hogging. “Working with Rockwell, it’s probably the most open solution,” Kleppek added. “The interface to a Rockwell PLC lets the CNC be a slave to a Rockwell PLC, or it can function as a master to other devices on the network.
“The interface is seamless, but there’s still the robot controller,” Kleppek said of the company’s CNC-Robot interface, “and it allows you to do parts set up and jog the robot from the CNC.” ME
This article was first published in the April 2014 edition of Manufacturing Engineering magazine. Click here for PDF.
Published Date : 4/1/2014